Security forces carried out many kidnappings and the government ignored most disappearances, adding to the anguish of families, Human Rights Watch reports.

A member of a caravan of Central American mothers holds a photograph of her… (Marco Ugarte, Associated…)

MEXICO CITY — Security forces have taken part in many kidnappings and disappearances in Mexico, and the government's failure to investigate most cases only compounds the anguish of their families, according to a scathing new human rights report.

The report released Wednesday serves as an indictment of the administration of former President Felipe Calderon, who left office Dec. 1, and poses urgent challenges for his successor, Enrique Peña Nieto.

Against the backdrop of a military-led offensive against powerful drug cartels, an estimated 70,000 people were killed during Calderon's six-year term, according to authorities and media tallies. Thousands more, possibly more than 20,000, disappeared.

The missing represent what U.S.-based Human Rights Watch called a festering unknown that causes enduring anguish for their families. More than a year of research by the group corroborated reporting by The Times and other news organizations, and stacks of complaints filed by families in almost every state of the republic.

Many of the missing were kidnapped by drug gangs, but all state security branches, including the military and federal and local police, are also accused of the "enforced disappearances" of many people, Human Rights Watch said. The Mexican navy, often praised by U.S. officials and others for its effectiveness in fighting drug gangs, also came in for serious criticism.

Involvement of the police and military highlights one of the key challenges that has historically bedeviled Mexico and now faces Peña Nieto. Efforts to clean up the country's notoriously corrupt police forces have had only limited success. And the military, as the government's main protagonist in the drug war, has been dragged into some of the same human rights abuses and corrupt practices that long corroded the police.

Calderon's government ignored the disappearances, failed to take steps to stop them and often blamed the victims, the report says.

"The result was the most severe crisis of enforced disappearances in Latin America in decades," Human Rights Watch said.

"What sets these crimes apart is that, for as long as the fate of the victim remains unknown, they are ongoing," the report says. "Each day that passes is another that authorities have failed to find victims, and another day that families continue to suffer the anguish of not knowing what happened to a loved one."

Human Rights Watch focused on 249 cases of men and women who have disappeared since 2006. In 149 cases, state security forces participated "directly in the crime, or indirectly through support or acquiescence," it said.

The findings were based on interviews with witnesses, families and authorities as well as documents, photographs and other material.

In one case that was examined earlier by The Times, 12 vendors of house paint vanished near a military checkpoint as they traveled to a job in the border city of Piedras Negras, in Coahuila state, in March 2009. In another, eight young men disappeared on a hunting trip in Zacatecas in December 2010.

"How can 12 people go missing, get rounded up, whatever happened, and no one notices?" Reyna Estrada, the wife of one of the Piedras Negras missing, said in an interview with The Times. "At least when your loved one dies, you know where they are, what happened, you can eventually get used to it. We do not know what monster we are fighting."

In several particularly chilling examples, the report concludes that authorities kidnapped people and then turned them over to drug gangs or other criminal networks. On May 28, 2011, the report says, 19 men on a construction crew in the Nuevo Leon town of Pesqueria were taken away by municipal police who were believed to have delivered them to a local crime boss.

The report documents the disappearances of at least 20 people who were seen being taken away by large convoys of naval special forces in June and July 2011.

The detentions took place over several states and with such precision that Human Rights Watch investigators believe they must have been part of a coordinated effort approved at high-ranking levels of the navy.

Both Human Rights Watch and the national Human Rights Commission, which also denounced several of the cases, say they have photographs and video of the sweeps. The navy at one point acknowledged detaining some of the people. The whereabouts of all remain unknown. No military personnel have been prosecuted in the cases.

Human Rights Watch said the cases it examined were a small sample, but that "there is no question that there are thousands more."

Atty. Gen. Jesus Murillo Karam said late last year that thousands of people disappeared during Calderon's administration. On Wednesday, a senior Interior Ministry official put the number at 27,000.